numerous applications because of their low manufacturing cost and simple open-loop position control capabilities. It is well known that their energy efficiency is low, although the actual efficiency values are generally not available. Moreover, the bulk of the stepping motors are driven in a nonoptimal way, e.g., in an open loop with a maximum current to avoid step loss and, thus, with low efficiency. In this article, the impact of the control algorithm on the efficiency of the motor is analyzed, measured, and discussed. The basic open-loop full-, half-, and microstepping algorithms are considered together with a more advanced vector control algorithm. For each algorithm, the torque/ current optimization is discussed. Stepping motors are typically used for multiple torque and speed operating points. To represent the efficiency of the motor at every operating point, isoefficiency curves are 1077-2618/14/$31.00©2014IEEE S the efficiency of hybrid Stepping MotorS the efficiency of hybrid Stepping MotorS B y S t I j n D E r a m m E l a E r E , B r a m V E r V I S c h , j o h a n n E S c o t t y n , B a r t V a n w a l l E g h E m , P E t E r c o x , F r E D E r I k D E B E l I E , k u r t S t o c k m a n , l I E V E n V a n D E analyzing the impact of control algorithms image licensed by ingram publishing IEEE Industry ApplIcAtIons MAgAzInE • July|Aug 2014 • www.IEEE.org/IAs 50 51 IEEE Industry ApplIcAtIons MAgAzInE • July|Aug 2014 • www.IEEE.org/IAsused. With these curves, the efficiencies of the motor, driven by different control strategies, can be compared.
The Energy Efficiency of Stepping Motor ApplicationsStepping motors are applied in the robotics, automotive, textile, and domestic apparatus industries, among many others. Their simple and cheap construction, ease of control, and open-loop capabilities make these motors very interesting in low-power applications. In addition, the absence of rotor windings reduces the inertia and weight so that high dynamics can be reached. Compared with dc-brush motors, the lack of contact aging serves the reliability and mechanical ruggedness. Finally, the availability of torque at a standstill makes a stepping motor perfectly suited for diverse applications.However, despite all of these advantages, stepping motor control algorithms, such as open-loop, full-step control, result in very poor torque/current ratios. These low torque/current ratios are reflected in a low overall efficiency [1]. Nowadays, research on energy-efficient electrical machines focuses on induction machines because of their great share in the consumed energy [2]- [5]. On the other hand, the energy efficiency of fractional horsepower drives, such as stepping motors, is unaddressed in the literature. Moreover, as these motors are frequently used for low-power position control, the efficiency seems to be irrelevant. However, the worldwide market for stepping motors is estimated at 17% of the total market for motor drivers [6]. It is obvious that the total amount of stepping motors installed worldwide is enorm...